Along with the development of science and technology, the amount of information transmission in modern communication systems increases rapidly, which requires higher capacity of transmission networks and a stronger ability of a network element to schedule traffics. In the middle of 90's, the WDM technology becomes a main technology in long-distance and region backbone transmission networks, and is applied in Metropolitan Area Networks (MANs) gradually. Traditional WDM systems employ separate device encapsulation, in which board cards are made around one or more optical devices, and the board cards are connected with each other through fibers.
With the development of technology, the price of optical devices is gradually reduced. However the cost of optical device encapsulation is still high, which is a bottleneck for the cost of optical devices. In a typical example, a core of a laser only needs several dollars, but its encapsulation costs hundreds of dollars.
In the last several years, people make efforts to integrate multiple optical devices such as a laser, a modulator and a multiplexing/de-multiplexing apparatus, so as to decrease the cost of optical devices. Additionally, the size of optical devices may be reduced as a result of decreasing encapsulation. At present, the optical integration technology is gradually mature, and is able to converge multiple single-wavelength signals into a multi-wavelength signal at one substrate and de-converge a multi-wavelength signal into multiple single-wavelength signals.
WDM devices may implement traffic transmission with large capacity. However, traditional WDM devices are mainly applied to point-to-point traffic transmission, and cannot implement flexible traffic scheduling. In order to improve the flexibility of traffic scheduling, new traffic scheduling technologies based on optical layer are put forward. Unfortunately, the cost of these traffic scheduling technologies based on optical layer is high, and the flexibility of traffic scheduling still cannot meet real requirements.
In order to provide more flexible network applications for the WDM devices, the traffic scheduling includes traffic scheduling in a wavelength plane and traffic scheduling in a sub-wavelength plane in the related art, and the wavelength traffic scheduling and sub-wavelength traffic scheduling are implemented by means of electric cross-connection.
FIG. 1 is a simplified diagram illustrating a structure of a conventional WDM node cross scheduling system. The system includes wavelength convergence/de-convergence module 101 in an input direction, wavelength scheduling matrix 102, wavelength convergence/de-convergence module 103 in an output direction, sub-wavelength convergence/de-convergence 104, and sub-wavelength scheduling matrix 105.
Wavelength convergence/de-convergence module 101 decomposes a multi-wavelength signal received from a WDM transmission line into multiple independent λ-wavelength signals, and transfers the multiple independent λ-wavelength signals to wavelength scheduling matrix 102.
Wavelength scheduling matrix 102 sends those λ-wavelength signals not needing to be performed sub-wavelength scheduling to wavelength convergence/de-convergence module 103 after performing uniform scheduling for the multiple independent λ-wavelength signals received from wavelength convergence/de-convergence module 101. Wavelength convergence/de-convergence module 103 sends the received λ-wavelength signals to an output line after converging the received λ-wavelength signals.
Wavelength scheduling matrix 102 sends those λ-wavelength signals needing to be performed sub-wavelength scheduling to sub-wavelength convergence/de-convergence module 104.
Sub-wavelength convergence/de-convergence module 104 decomposes the received λ-wavelength signals into sub-wavelength traffics independent from each other, and sends the sub-wavelength traffics to sub-wavelength scheduling matrix 105.
Sub-wavelength scheduling matrix 105 performs the sub-wavelength scheduling for the received sub-wavelength traffics.
In the related art, a two-level scheduling structure is used, in which wavelength scheduling matrix 102 and sub-wavelength scheduling matrix 105 are combined. Thus, a channel must be provided to interconnect wavelength scheduling matrix 102 and sub-wavelength scheduling matrix 105. It can be seen from the system as shown in FIG. 1 that sub-wavelength convergence/de-convergence module 104 is configured between wavelength scheduling matrix 102 and sub-wavelength scheduling matrix 105 as a interconnecting channel, which results in the low integration and utilization rate of the network node cross scheduling system and the high hardware cost of the network node cross scheduling system.
Additionally, the interconnecting channel between wavelength scheduling matrix 102 and sub-wavelength scheduling matrix 105 becomes a bottleneck of traffic scheduling and greatly reduces the access ability of the network node cross scheduling system. In order to guarantee the flexibility of traffic scheduling in the network node cross scheduling system, an interconnecting channel with a bandwidth large enough must be designed. However, the larger the bandwidth of the interconnecting channel is, the higher the cost of the interconnecting channel is.